title: Nucleotide pyrophosphatase/phosphodiesterase 1 exerts a negative effect on starch accumulation and growth in rice seedlings under high temperature and CO2 concentration conditions.
abstract: Nucleotide pyrophosphatase/phosphodiesterase (NPP) is a widely distributed enzymatic activity occurring in both plants and mammals that catalyzes the hydrolytic breakdown of the pyrophosphate and phosphodiester bonds of a number of nucleotides. Unlike mammalian NPPs, the physiological function of plant NPPs remains largely unknown. Using a complete rice NPP1-encoding cDNA as a probe, in this work we have screened a rice shoot cDNA library and obtained complete cDNAs corresponding to six NPP genes (NPP1-NPP6). As a first step to clarify the role of NPPs, recombinant NPP1, NPP2 and NPP6 were purified from transgenic rice cells constitutively expressing NPP1, NPP2 and NPP6, respectively, and their enzymatic properties were characterized. NPP1 and NPP6 exhibited hydrolytic activities toward ATP, UDP-glucose and the starch precursor molecule, ADP-glucose, whereas NPP2 did not recognize nucleotide sugars as substrates, but hydrolyzed UDP, ADP and adenosine 5'-phosphosulfate. To gain insight into the physiological function of rice NPP1, an npp1 knockout mutant was characterized. The ADP-glucose hydrolytic activities in shoots of npp1 rice seedlings were 8% of those of the wild type (WT), thus indicating that NPP1 is a major determinant of ADP-glucose hydrolytic activity in rice shoots. Importantly, when seedlings were cultured at 160 Pa CO2 under a 28°C/23°C (12 h light/12 h dark) regime, npp1 shoots and roots were larger than those of wild-type (WT) seedlings. Furthermore, the starch content in the npp1 shoots was higher than that of WT shoots. Growth and starch accumulation were also enhanced under an atmospheric CO2 concentration (40 Pa) when plants were cultured under a 33°C/28°C regime. The overall data strongly indicate that NPP1 exerts a negative effect on plant growth and starch accumulation in shoots, especially under high CO2 concentration and high temperature conditions.
authors.affiliation: Department of Applied Biological Chemistry, Niigata University, 2-8050 Ikarashi, Niigata, 950-2181 Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kaneko
authors.forename: Takuya
authors.initials: T
authors.lastname: Inomata
authors.forename: Takahiro
authors.initials: T
authors.lastname: Masui
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Koshu
authors.forename: Yukiho
authors.initials: Y
authors.lastname: Umezawa
authors.forename: Kimiko
authors.initials: K
authors.lastname: Itoh
authors.forename: Javier
authors.initials: J
authors.lastname: Pozueta-Romero
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Mitsui
mesh_terms: D000245:Adenosine Diphosphate Glucose / Q000378:metabolism; D001483:Base Sequence; D002245:Carbon Dioxide / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D011755:Pyrophosphatases / Q000235:genetics / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D017422:Sequence Analysis, DNA; D013213:Starch / Q000378:metabolism*; D013696:Temperature
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; D002245:Carbon Dioxide; D000245:Adenosine Diphosphate Glucose; D013213:Starch; D010727:Phosphoric Diester Hydrolases; D011755:Pyrophosphatases; C021899:nucleotide pyrophosphatase
keywords: ADP-glucose; CO2; NPP; Oryza sativa; Plastid; Starch